|
|
||
|
|
|
|
Fig. 2: Cross-sectional morphologies of hollow fibers spun with different polymer solutions (17/13/70, 17/7/76 and 17/0/83 PEI/DEG//NMP), using 50/50 water/EG internal fluid at flow rates of 2 ml/min and 3 ml/min.
The elastic inner cylindrical shell could be buckled into a number of circumferential waves when the overall external radial pressure reaches its critical values. This pressure is the sum of the partial pressure generated by the internal fluid in lumen (P1, negative), by the fluid flow with varying density in the middle region (P2, positive) and by the shrinkage of the polymer outer layer under a collection speed (P3, positive).
(I guess “positive” pressure is external to the inner shell and “negative” pressure is internal to the inner shell.)
FROM:
Ngoc Lieu Le, Dooli Kim and Suzana P. Nunes (King Abdullah University of Science and Technology (KAUST), Biological and Environmental Science and Engineering Division (BESE), Thuwal, Saudi Arabia),
“Evolution of regular geometrical shapes in fiber lumens”, Scientific Reports, Vol. 7, Article number: 9171, August 2017, doi:10.1038/s41598-017-09134-z
ABSTRACT: The geometry of polymeric hollow fibers for hemodialysis or desalination is a key factor determining their performance. Deformations are frequently observed, but they are rather random. Here we were able to exactly control the shape evolution of the internal channels or lumens of polymeric hollow fibers, leading to polygonal geometries with increasing number of sides. The elasticity of the incipient channel skin and instabilities during fiber formation are affected by the internal coagulant fluid composition and flow rate; and highly influence the polygonal shape. We propose a holistic explanation by analyzing the thermodynamic, kinetic and rheological aspects involved in the skin formation and their synergy.
Page 140 / 360